2. Introduction- Honing
• Honing is an abrasive machining process that produces a
precision surface on a metal workpiece by scrubbing an
abrasive stone against it along a controlled path.
• Honing is primarily used to improve the geometric form of a
surface, but may also improve the surface texture.
• Hone tool has a combined motion of rotation and
translation
3. Application
• Cylinders for internal combustion engines, air bearing
spindles and gears.
• There are many types of hones but all consist of one or
more abrasive stones that are held under pressure against
the surface they are working on.
• In terms of sharpening knives, a honing steel does not
actually hone knives, but simply realigns the metal along the
edge.
6. Honing Stone
• The hone is composed of abrasive grains that are bound
together with an adhesive.
• Generally, honing grains are irregularly shaped and about 10 to
50 micrometers in diameter (300 to 1,500 mesh grit).
• Smaller grain sizes produce a smoother surface on the
workpiece.
• A honing stone is similar to a grinding wheel in many ways, but
honing stones are usually more friable so that they conform to
the shape of the workpiece as they wear in. To counteract
their friability, honing stones may be treated with wax or sulfur
to improve life; wax is usually preferred for environmental
reasons.
• Any abrasive material may be used to create a honing stone,
but the most commonly used are corundum, silicon carbide,
cubic boron nitride, or diamond
7. Electrochemical Machining(ECM)
• It is a method of removing metal by an electrochemical
process.
• It is normally used for mass production and is used for
working extremely hard materials or materials that are
difficult to machine using conventional methods.
• Its use is limited to electrically conductive materials.
• ECM is often characterized as "reverse electroplating," in
that it removes material instead of adding it. It is similar in
concept to electrical discharge machining (EDM)
• In ECM there is no tool wear. The ECM cutting tool is guided
along the desired path close to the work but without
touching the piece.
8. Electrochemical Machining(ECM)
• High metal removal rates are possible with ECM, with no
thermal or mechanical stresses being transferred to the
part, and mirror surface finishes can be achieved.
• In the ECM process, a cathode (tool) is advanced into an
anode (workpiece). The pressurized electrolyte is injected at
a set temperature to the area being cut. The feed rate is the
same as the rate of "liquefaction" of the material. The gap
between the tool and the workpiece varies within 80-800
micrometers (.003 in. and .030 in.).
• As electrons cross the gap, material from the workpiece is
dissolved, as the tool forms the desired shape in the
workpiece. The electrolytic fluid carries away the metal
hydroxide formed in the process.
10. Electrochemical Honing
• It is a process in which it combines the high removal
characteristics of Electrochemical Dissolution(ECD) and
Mechanical Abrasion(MA) of conventional Honing.
• It has much higher rates than either of honing & internal
cylindrical grinding.
• Cathodic tool is similar to the conventional honing tool, with
several rows of small holes so that electrolyte could enter
directly into interelectrode gap.
• Electrolyte provides electron through the ionization process
which acts as coolant and flushes away the chips that are
formed off by mechanical abrasion and metal sludge that
results from electrochemical dissolution action.
11. Electrochemical Honing-Process
• Tool is inserted inside the worked hole or a cylinder.
• Mechanical abrasion takes place first by the stones/hones.
• Oxides formed due to working from previous process will be
removed by it and clean surface will be achieved.
• Now the clean surface will be in contact with electrolyte and
then Electrochemical Dissolution will remove the desired
material.
• Same procedure is continued till the required cut is made.
• To control surface roughness Mechanical Abrasion is
allowed to continue for a few seconds after the current has
been turned off.
12. Electrochemical Honing-Process
• Majority of the material is removed by the ECD phase.
• Abrading stones remove enough material to generate a
round, straight, geometrically true cylinder.
• Mechanical abrasion just removes the surface oxides that
are formed on the work surface due to ECD.
• Removal of oxides enhances the performance of ECD as it
could directly remove the required material and fresh
surface is obtained for each ECD phase.
13.
14.
15. Process Characteristics
• Abrasive stones are used to maintain the gap size of 0.075
to 0.250mm.
• Surface finish ranges from: 0.2 to 0.8µm.
• Electrolyte temperature is nearly maintained at 38-40 0C.
• Pressure of 1000kPa.
• Flow Rate: 95 L/min.
• DC Current is Used.
• Voltage gap of 6 to 30V is kept accordingly.
• Current Density of 465 A/cm2 .
16. Process Characteristics
• Cross-Hatched Cut surface is obtained after machining
which is most desired after any load bearing surface.
• Tolerance can be achieved is as low as ±0.003mm.
• Material removal rate is 3 to 5 times faster then
conventional honing and 4 times faster than that of internal
cylindrical grinding.
17. Applications
• Due to rotating and reciprocating honing motion, the
process reduces the errors in roundness through the rotary
motion.
• Taper and waviness errors can also be reduced
18.
19. Advantages
• Low tolerances.
• Good surface finish is achieved.
• Small Correction on workpieces is possible.
• Shaping and surface finishing is done in one process.
• Light stone/hone pressure is used in the process, heat
distortion is avoided.
• Due to Electrochemical Dissolution phase, no stress is
accumulated and it automatically deburrs the part.
• It can be used for hard and conductive material that are
susceptible to heat and distortion.
